Overlay error measurement device and method

Abstract

The application provides a kind of overlay error measurement device and method, the overlay error measurement device includes illumination unit, light splitting device, objective lens, first detection unit and data processor.The first detection unit includes first aperture stop, and the first aperture stop includes at least one adjustable through hole.Adjust the through hole, when the first aperture stop is first state, the first detector obtains first signal and transmits to the data processor, when the first aperture stop is second state, the first detector obtains second signal and transmits to the data processor.The first signal is calibration signal, the second signal is calibrated by the first signal, and the overlay error is calculated using the calibrated second signal.Therefore, using the overlay error measurement device and method can obtain more accurate overlay error, so as to improve the detection performance of overlay error measurement device and improve work efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of integrated circuit manufacturing, and in particular to a kind of overlay measurement device and method. BACKGROUND

[0002] According to the lithography measurement technology roadmap given by International Technology Roadmap for Semiconductors (ITRS), with the lithography pattern critical dimension (CD) into 22nm and below process node, especially the application and development of Double Patterning and extreme ultraviolet lithography technology (EUVL), the measurement precision requirement of lithography process parameter overlay has entered the sub-nanometer field. Due to the limit of imaging resolution limit, the traditional overlay measurement technology based on imaging and image recognition (Imaging-Based overlay, IBO) has gradually cannot meet the requirements of new process node to overlay measurement, and the overlay measurement technology based on diffraction light detection (Diffraction-Based overlay, DBO) and the overlay measurement technology based on micro-mark diffraction light detection (uDBO) are gradually becoming the main means of overlay measurement.

[0003] But in the commonly used overlay error measurement device or method, the influence of the non-uniformity of measurement illumination spot itself on overlay error is often ignored, or the calibration overlay mark is moved to be located at multiple different positions of measurement illumination spot, and the system is calibrated according to sample measurement results, but due to too little sampling data, the characteristics of the mark used for calibration are not easy to control, the calibration effect for the non-uniformity of illumination spot itself is poor, and the calibration process is complex and time-consuming.

[0004] Therefore, an overlay error measurement system and method are needed, which can realize more accurate calibration of the non-uniformity of measurement illumination spot itself, so as to improve the detection performance of overlay error measurement device and obtain more accurate overlay error. SUMMARY

[0005] The present application aims to provide an overlay error measurement device and method to solve the influence of the non-uniformity of measurement illumination spot itself on overlay error measurement.

[0006] To solve the above technical problems, the present application provides an overlay error measurement device, which comprises an illumination unit, a light splitting device, an objective lens, a first detection unit and a data processor; the illumination unit is used to provide light illumination of two or more different light illumination modes; the light splitting device comprises a first light splitting plate and a second light splitting plate;

[0007] The light provided by the illumination unit is transmitted to the first substrate or the second substrate through the first beam splitter and the objective lens, and after being reflected by the first substrate or the second substrate, the light forms a first light beam after being transmitted through the objective lens, the first beam splitter and the second beam splitter, and the first light beam is transmitted to the first detection unit;

[0008] The first detection unit comprises a first aperture stop and a first detector, the first aperture stop comprises at least one adjustable through hole, and the first light beam is transmitted to the first detector through the first aperture stop; when the light is reflected by the first substrate and the first aperture stop is in a first state by adjusting the through hole, the first detector outputs a first signal to the data processor; when the light is reflected by the second substrate and the first aperture stop is in a second state by adjusting the through hole, the first detector outputs a second signal to the data processor;

[0009] The data processor is configured to calculate the overlay error according to the first signal and the second signal.

[0010] Optionally, in the overlay error measurement device, when the light is transmitted in the direction from the objective lens to the first aperture stop, the effective first numerical aperture of the objective lens is greater than 0.5 when the first aperture stop is in the first state, and the effective first numerical aperture of the objective lens is less than or equal to 0.5 when the first aperture stop is in the second state.

[0011] Optionally, in the overlay error measurement device, when the light is transmitted in the direction from the objective lens to the first substrate or the second substrate, the second numerical aperture of the objective lens is greater than or equal to 0.9, and the first numerical aperture is less than the second numerical aperture.

[0012] Optionally, in the overlay error measurement device, the illumination unit comprises a light source, an illumination collimator, a second aperture stop and an illumination relay;

[0013] The light source is configured to provide light;

[0014] The illumination collimator is configured to modulate the light provided by the light source;

[0015] The second aperture stop is configured to change the light mode of the light modulated by the illumination collimator;

[0016] The illumination relay is configured to transmit the light of the second aperture stop to the first beam splitter.

[0017] Optionally, in the overlay error measurement device, the illumination unit further comprises a motorized turntable, the illumination unit comprises at least two second aperture stops, and the motorized turntable is configured to switch between different second aperture stops to change the illumination mode of the light modulated by the illumination collimator.

[0018] Optionally, in the overlay error measurement device, the first probe unit further comprises an imaging relay and an imaging lens group, and the imaging relay, the first aperture stop, the imaging lens group and the first detector are arranged in sequence.

[0019] The imaging relay is configured to transmit the first light beam after the second light splitting plate splits the light to the first aperture stop.

[0020] The imaging lens group is configured to image the first light beam passing through the first aperture stop on the first detector.

[0021] Optionally, in the overlay error measurement device, the first signal is the zero-order diffraction light intensity distribution of the first light beam, and the second signal is the positive first-order diffraction light intensity distribution and the negative first-order diffraction light intensity distribution of the first light beam.

[0022] Optionally, in the overlay error measurement device, a plurality of sample positions are selected on the second substrate, each sample position comprises at least four marker units, each marker unit is provided with a measurement marker, the measurement marker comprises a first measurement marker and a second measurement marker, the first measurement marker and the second measurement marker correspond to each other, and the first measurement marker is provided with a preset offset relative to the second measurement marker, the preset offset comprises a first direction preset offset and / or a second direction preset offset, and the first direction and the second direction are perpendicular to each other.

[0023] Optionally, in the overlay error measurement device, the first measurement marker and the second measurement marker are both gratings, and the light transmitted by the objective lens diffracts through the gratings to generate multiple-order diffraction light.

[0024] Optionally, in the overlay error measurement device, the overlay error measurement device further comprises the second probe unit, and the second probe unit comprises an angular spectrum imaging assembly and a second detector.

[0025] The light further forms a second light beam after passing through the objective lens, the first light splitting plate and the second light splitting plate, the second light beam is transmitted to the second detector through the angular spectrum imaging assembly, the second detector outputs a third signal to the data processor, and the data processor monitors the energy fluctuation of the light on the first substrate or the second substrate according to the third signal.

[0026] Based on the same inventive concept, the present application also provides a method for measuring overlay error, comprising:

[0027] Step one: adjusting the illumination unit to a first illumination mode and the first aperture stop to a first state, measuring a first substrate, the first probe acquiring a first signal under the first illumination mode and transmitting to a data processor;

[0028] Step two: adjusting the illumination unit to a second illumination mode and the first aperture stop to the first state, measuring the first substrate, the first probe acquiring a first signal under the second illumination mode and transmitting to the data processor;

[0029] Step three: adjusting the illumination unit to the first illumination mode and the first aperture stop to a second state, measuring a sample position on a second substrate, the second substrate being pre-provided with a plurality of sample positions, the first probe acquiring a second signal under the first illumination mode and transmitting to the data processor;

[0030] Step four: adjusting the illumination unit to the second illumination mode and the first aperture stop to the second state, measuring the sample position on the second substrate, the first probe acquiring a second signal under the second illumination mode and transmitting to the data processor;

[0031] Step five: measuring another sample position on the second substrate, repeating steps three to four until all sample positions are measured; the data processor calibrating the second signal under the first illumination mode according to the first signal under the first illumination mode, and calibrating the second signal under the second illumination mode according to the first signal under the second illumination mode, and calculating the overlay error of the second substrate according to the calibrated second signal under the first illumination mode and the calibrated second signal under the second illumination mode.

[0032] Optionally, in the method for measuring overlay error, in the step one, the first signal under the first illumination mode is a zero-order diffraction light intensity distribution under the first illumination mode.

[0033] Optionally, in the method for measuring overlay error, in the step two, the first signal under the second illumination mode is a zero-order diffraction light intensity distribution under the second illumination mode.

[0034] Optionally, in the method for measuring overlay error, in the step three, the second signal under the first illumination mode is a positive first-order diffraction light intensity distribution of the sample position on the second substrate.

[0035] Optionally, in the overlay error measurement method, in the step four, the second signal under the second illumination mode is a first order negative diffraction light intensity distribution of the sample position on the second substrate.

[0036] Optionally, in the overlay error measurement method, the first signal and the second signal are measured multiple times and averaged.

[0037] Optionally, in the overlay error measurement method, in the step three, a plurality of sample positions are preset on the second substrate, each of the sample positions comprises at least four mark units, each of the mark units is provided with a measurement mark, the measurement mark comprises a first measurement mark and a second measurement mark, the first measurement mark and the second measurement mark correspond to each other, and the first measurement mark is provided with a preset offset relative to the second measurement mark, the preset offset comprises a preset offset in a first direction and / or a preset offset in a second direction; wherein the preset offsets of at least two mark units in the first direction are opposite in direction but equal in value, and the preset offsets of at least two mark units in the second direction are opposite in direction but equal in value; the first direction and the second direction are perpendicular to each other.

[0038] Optionally, in the overlay error measurement method, the asymmetry of the mark unit is obtained by the following formula:

[0039]

[0040]

[0041] is the first order positive diffraction light intensity distribution corresponding to the i-th mark unit after calibration;

[0042] is the first order negative diffraction light intensity distribution corresponding to the i-th mark unit after calibration;

[0043] is the first order positive diffraction light intensity distribution corresponding to the i+1-th mark unit after calibration;

[0044] is the first order negative diffraction light intensity distribution corresponding to the i+1-th mark unit after calibration;

[0045] A i is the asymmetry of the i-th mark unit;

[0046] A i+1 is the asymmetry of the i+1-th mark unit;

[0047] The preset offset on the i-th marking unit and the i+1-th marking unit is equal in value but opposite in direction in a first direction or a second direction, and the first direction and the second direction are perpendicular to each other.

[0048] Optionally, in the overlay error measurement method, the data processor calculates the overlay error in the first direction or the second direction at each sample position by the following formula:

[0049]

[0050] A i is the asymmetry of the i-th marking unit;

[0051] A i+1 is the asymmetry of the i+1-th marking unit;

[0052] Δ is a preset offset;

[0053] ε is an overlay error.

[0054] In summary, the present application provides an overlay error measurement device and method. The overlay error measurement device comprises an illumination unit, a light splitting device, an objective lens, a first detection unit and a data processor. The first detection unit comprises a first aperture stop, and the first aperture stop comprises at least one adjustable through hole. The through hole is adjusted. When the first aperture stop is in a first state, the first detector acquires a first signal and transmits it to the data processor. When the first aperture stop is in a second state, the first detector acquires a second signal and transmits it to the data processor. The first signal can be used as a calibration signal. The second signal is calibrated by the first signal, and the calibrated second signal is used to calculate the overlay error. The non-uniformity of the light provided by the illumination unit is compensated. Thus, the overlay error measurement device and method can obtain more accurate overlay error, thereby improving the detection performance of the overlay error measurement device and improving the work efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 is a one-dimensional grating diffraction schematic diagram when the overlay error of the embodiment of the present application is zero;

[0056] Figure 2 is a one-dimensional grating diffraction schematic diagram when the overlay error of the embodiment of the present application is less than zero;

[0057] Figure 3 is a one-dimensional grating diffraction schematic diagram when the overlay error of the embodiment of the present application is greater than zero;

[0058] Figure 4 is a two-dimensional grating diffraction schematic diagram when the overlay error of the embodiment of the present application is less than zero in the X-axis direction and less than zero in the Y-axis direction.

[0059] Figure 5 is a two-dimensional grating diffraction schematic diagram of an embodiment of the present application, in which overlay error X-axis direction is greater than zero and Y-axis direction is less than zero;

[0060] Figure 6 is a two-dimensional grating diffraction schematic diagram of an embodiment of the present application, in which overlay error X-axis direction is less than zero and Y-axis direction is greater than zero;

[0061] Figure 7 is a two-dimensional grating diffraction schematic diagram of an embodiment of the present application, in which overlay error X-axis direction is greater than zero and Y-axis direction is greater than zero;

[0062] Figure 8 is an overlay mark located at different positions of an embodiment of the present application;

[0063] Figure 9 is a schematic diagram of connection of each module of an overlay error measurement system of an embodiment of the present application;

[0064] Figure 10 is a schematic diagram of structure of an overlay error measurement system of an embodiment of the present application;

[0065] Figure 11 is a first aperture stop schematic diagram of an embodiment of the present application;

[0066] Figure 12 is a mark unit schematic diagram of an embodiment of the present application;

[0067] In which, the reference signs are explained as follows:

[0068] M1-first substrate; M2-second substrate;

[0069] 1-first measurement mark; 2-second measurement mark; 3-overlay error measurement device;

[0070] 30-illumination unit; 31-splitting device; 32-objective; 33-second detection unit; 34-first detection unit; 35-data processor;

[0071] 301-second aperture stop; 302-light source; 303-illumination collimator; 304-illumination relay; 3011-second aperture stop of first light illumination mode; 3012-second aperture stop of second light illumination mode;

[0072] 311-first splitting plate; 312-second splitting plate;

[0073] 331-second detector; 332-angular spectrum imaging assembly;

[0074] 341 - first aperture stop; 3411 - first through-hole; 3412 - second through-hole; 3413 - third through-hole; 342 - imaging relay; 343 - imaging lens group; 344 - first detector;

[0075] 5 - sample position; 51 - first marking unit; 52 - second marking unit; 53 - third marking unit; 54 - fourth marking unit;

[0076] a - first light beam; b - second light beam. DETAILED DESCRIPTION

[0077] As described above, in the commonly used device or method for measuring overlay error, the influence of the non-uniformity of the measurement illumination spot itself on the overlay error is often ignored, or the calibration overlay mark is moved to be located at multiple different positions of the measurement illumination spot, and the system is calibrated according to the sample measurement results. However, due to too few sampling data, the characteristics of the mark used for calibration are not easy to control, the calibration effect for the non-uniformity of the illumination spot itself is poor, and the calibration process is complex and time-consuming.

[0078] Therefore, there is a need for an overlay error measurement device and method which can realize more accurate calibration for the non-uniformity of the measurement illumination spot itself, thereby improving the detection performance of the lithography machine and obtaining more accurate overlay error.

[0079] The overlay error measurement device and method proposed by the present application will be further described in detail below in combination with the drawings and specific embodiments. The advantages and features of the present application will be clearer according to the following description. It should be noted that the drawings are all very simplified and use non-precise proportions, only for the purpose of facilitating and clarifying the description of the embodiments of the present application. In addition, the structures shown in the drawings are often part of the actual structures. In particular, the emphasis of each drawing is different, and sometimes different proportions are used.

[0080] In a one-dimensional grating mark, as shown in the upper grating of Figure 1 , which is the first measurement mark 1, obtained by second exposure, generally photoresist. The middle layer is the intermediate process, which can be Si3N4 film, etc., and the lower grating is the second measurement mark 2, obtained by first exposure, generally silicon as the substrate material. When the second exposure cannot completely coincide with the first exposure, a relative displacement will be generated between the upper and lower gratings, and this displacement amount is the overlay error ε. As shown in Figure 1 , the overlay error ε = 0, as shown in Figure 2 , ε < 0, and as shown in Figure 3 , ε > 0. When the incident light is projected into the grating, reflection will occur, and the reflected light will diffract when passing through the grating layer with multiple slits, generating multiple-order diffracted light. Among them, I0 represents the zero-order diffracted light, I + , I- Let A and B represent the +1st and -1st order diffracted beams, respectively. When the overlay error ε = 0, the intensity of the ±1st order diffracted beams is symmetrical; when the overlay error ε ≠ 0, the intensity of the ±1st order diffracted beams is asymmetrical. Therefore, the asymmetry is defined as A = I. + -I - Within a certain range, the overlay error ε and the asymmetry satisfy a linear relationship, that is, A is approximately proportional to the positional offset x of the upper and lower markings, and the relationship is A(x)=kx, where k is a constant related to the marking manufacturing process.

[0081] In two-dimensional raster markings, such as Figures 4-7 As shown, the first measuring mark 1 and the second measuring mark 2 are respectively provided with a preset offset Δ and a scaling error ε in the first direction and the second direction, that is, in the X-axis and Y-axis directions. In the X-axis direction, the scaling error is ε, and in the Y-axis direction, the scaling error is ε'. The preset offsets set in the same axis direction are opposite. Therefore, as... Figure 4 and Figure 5 As shown, the asymmetries A in the X-axis direction are: A1(-Δ+ε)=k(-Δ+ε), A2(Δ+ε)=k(Δ+ε); Figure 6 and Figure 7 As shown, the asymmetries A in the Y-axis direction are: A3-Δ+ε'=k-Δ+ε', A4(Δ+ε')=k(Δ+ε'), according to A=I + -I - We can obtain:

[0082] In the X-axis direction:

[0083]

[0084]

[0085]

[0086] In the Y-axis direction:

[0087]

[0088]

[0089]

[0090] Therefore, by measuring with equipment The overprinting error ε in the X-axis direction and the overprinting error ε' in the Y-axis direction can then be calculated.

[0091] But the measurement of light exists uneven light, that is, the incident light intensity of different positions in the measurement field is not equal, which will have a great influence on the collection of ±1 order diffraction light, which will directly affect the accuracy of overlay error.

[0092] As shown in Figure 8 , in the measurement field under the same measurement light, the mark unit O1 and the mark unit O2 are opposite in the preset offset direction of the X axis, and the size is Δ=10nm. When the mark unit O1 and the mark unit O2 are located at N1 position, the zero order diffraction light I 01 at the mark unit O1 is normalized to 1, the positive first order diffraction light is 1000, and the negative first order diffraction light is 892; the zero order diffraction light I 02 at the mark unit O2 is normalized to 1.008, the positive first order diffraction light is 850, and the negative first order diffraction light is 1050, so A1=108, A2=-200, and ε=92 / 308*10nm=2.987nm.

[0093] When the mark unit O1 and the mark unit O2 are located at N2 position, the zero order diffraction light I 01 at the mark unit O1 is normalized to 1.0065, the positive first order diffraction light is 1000*1.0065=1000.65, and the negative first order diffraction light is 892*1.0065=897.798; the zero order diffraction light I 02 at the mark unit O2 is normalized to 1.0033, the positive first order diffraction light is 850 / 1.008*1.0033=846.0367, and the negative first order diffraction light is 1050 / 1.008*1.0033=1045.1, so A1'=102.852, A2'=-199.0633, and ε'=96.2113 / 301.9153*10nm=3.187nm. The difference between N1 and N2 measurements will reach 0.2nm, and the total measurement repeatability requirement of the device is 0.4nm.

[0094] It can be seen that the uneven distribution of light intensity has a great influence on the detection of overlay error. Therefore, when measuring ±1 order diffraction light, the uneven distribution information of incident light intensity needs to be collected in advance as a calibration variable to improve the accuracy of overlay error. Therefore, the overlay error measurement device proposed in this embodiment collects the zero order diffraction light as a calibration variable for unevenness of measurement light, and calculates the overlay error value after data calibration.

[0095] Please refer toFigure 9 and Figure 10 The overlay error measuring device 3 includes an illumination unit 30, a beam splitter 31, an objective lens 32, a first detection unit 34, and a data processor 35. The illumination unit 30 provides illumination in two or more different illumination modes. The beam splitter 31 includes a first beam splitter 311 and a second beam splitter 312. The illumination provided by the illumination unit 30 is transmitted through the first beam splitter 311 and the objective lens 32 to the first substrate M1 or the second substrate M2, and after reflection from the first substrate M1 or the second substrate M2, it is transmitted to the objective lens 32 and the first beam splitter 311. After passing through the second beam splitter 312, a first beam a is formed, and the first beam a is transmitted to the first detection unit 34.

[0096] The first detection unit 34 includes a first aperture stop 341 and a first detector 344. The first aperture stop 341 includes at least one adjustable through-hole. The first light beam a is transmitted to the first detector 344 through the first aperture stop 341. When the first aperture stop 341 is in a first state by adjusting the through-hole, the first detector 344 outputs a first signal to the data processor 35. When the first aperture stop 341 is in a second state by adjusting the through-hole, the first detector 344 outputs a second signal to the data processor 35. The data processor 35 is used to calculate the overlay error based on the first signal and the second signal.

[0097] The lighting unit 30 is equipped with a second aperture stop 301. Switching the second aperture stop 301 enables different lighting modes. Switching the second aperture stop 301 can be achieved by a motorized turntable driving multiple second aperture stops 301, or by using a shutter for high-speed switching. Figure 10 As shown, the second aperture stop 3011 and the second aperture stop 3012 can provide two different illumination modes. When switched to the second aperture stop 3011, it is the first illumination mode, which can collect the positive first-order diffraction light of the overlay measurement mark; when switched to the second aperture stop 3012, it is the second illumination mode, which can collect the negative first-order diffraction light of the overlay measurement mark.

[0098] The illumination unit 30 further comprises a light source 302, an illumination collimator 303 and an illumination relay 304. The light source 302 provides illumination, which can be a mercury lamp, a xenon lamp or a mixture of deuterium lamp and halogen lamp, or a white LED or a plasma excitation light source, etc. The illumination collimator 303 comprises a collimator, a filter and a polarizer (not shown), and is used to modulate the incident light from the light source 302, mainly to modulate the wavelength, illumination mode, etc., so as to improve the process adaptability and signal-to-noise ratio of the system. The illumination relay 304 is used to transmit the incident light from the second aperture diaphragm 301 to the light splitting device 31. Since the pupil plane of a general microscope objective is located inside the objective, the illumination needs to be transmitted through the illumination relay unit 304.

[0099] The light splitting device 31 comprises a first light splitting plate 311 and a second light splitting plate 312. The first light splitting plate 311 is used to reflect the illumination provided by the illumination unit 30 to the surface of the substrate M, and the second light splitting plate 312 is used to split the reflected light from the surface of the substrate M into a first light beam a and a second light beam b for light transmission. Both the first light beam a and the second light beam b represent the surface information of the first substrate M1 and / or the second substrate M2.

[0100] The illumination is incident on the first substrate M1 or the second substrate M2 through the objective 32, and the reflected light from the first substrate M1 or the second substrate M2 is transmitted to the light splitting device 31 through the objective 32. When the illumination is transmitted along the direction from the objective 32 to the first substrate M1 or the second substrate M2, the second numerical aperture of the objective is greater than or equal to 0.9. When the illumination is transmitted along the direction from the objective 32 to the first aperture diaphragm 341, and the first aperture diaphragm 341 is in the first state, i.e., the zero-order diffracted light can pass through the first aperture diaphragm 341, the effective first numerical aperture of the objective is greater than 0.5; when the first aperture diaphragm is in the second state, i.e., the zero-order diffracted light is blocked and cannot pass through the first aperture diaphragm 341, the effective first numerical aperture of the objective 32 is less than or equal to 0.5.

[0101] The first detection unit 34 further comprises an imaging relay 342 and an imaging lens group 343. The first aperture diaphragm 341 has more than one through hole, and the aperture of each through hole can be adjusted to multiple sizes. As shown in the first aperture diaphragm 341 having two through holes, a first through hole 3411 and a second through hole 3412, the first through hole 3411 can pass the zero-order diffracted light, and the second through hole 3412 can pass the positive and negative first-order diffracted light, and block the zero-order diffracted light. Figure 10 Figure 11 ​The first aperture stop 341 has a third through hole 3413, and the sizes of the first through hole 3411 and the second through hole 3412 can be modulated by the third through hole 3413. The imaging relay 343 is used to transmit the first light beam a to the first aperture stop 341. The imaging lens group 343 is used to image the light passing through the first aperture stop 341 on the first detector 344. The first detector 344 is used to acquire the zero-order diffraction light intensity distribution carried by the first light beam a as a first signal and the positive first-order diffraction light intensity distribution and the negative first-order diffraction light intensity distribution as a second signal, and transmit them to the data processor 35.

[0102] The data processor 35 receives the first signal and the second signal acquired by the second detection unit 33, and calculates the overlay error.

[0103] The overlay error measurement device 3 further includes the second detection unit 33, which includes an angular spectrum imaging assembly 332 and a second detector 331. The angular spectrum imaging assembly 332 in the second detection unit 33 includes a diffraction element and a receiving screen. The reflected light transmitted by the second light beam b moves to the receiving screen through the diffraction element. The second detector 331 acquires the angular spectrum of the reflected light and calculates a third signal representing the surface light intensity distribution of the first substrate M1 and / or the second substrate M2 through Fourier transform. The second detector 331 transmits the third signal to the data processor 35. The third signal is used to represent the energy fluctuation of the illumination on the surface of the first substrate M1 and / or the second substrate M2, and assist in optimizing the system configuration.

[0104] Based on the same inventive concept, the embodiment further provides an overlay error measurement method, which includes:

[0105] Step one: adjust the through hole of the second aperture stop of the illumination unit 30 to be 3011, and the illumination mode is the first illumination mode. The through hole size of the first aperture stop 341 is adjusted to be the first state 3411.

[0106] The illumination provided by the illumination unit 30 enters the beam splitter 31. The first beam splitter plate 311 of the beam splitter 31 reflects the illumination to the objective lens 32. The objective lens 32 transmits the illumination to the surface of the first substrate M1. The surface of the first substrate M1 reflects the reflected light.

[0107] The reflected light enters the light splitting device 31 through the objective lens 32, and forms a first light beam a through the second light splitting plate 312 of the light splitting device 31, which enters the first detection unit 34. The first detector 344 takes a photo to obtain a first signal in the first light illumination mode, i.e., a zero-order diffraction light intensity distribution in the first light illumination mode, and then transmits to the data processor 35.

[0108] Step two: adjust the aperture of the second aperture stop of the illumination unit 30 to 3012, the illumination mode is the second light illumination mode, keep the aperture size of the first aperture stop 341 as the first state 3411, the first detector 344 takes a photo to obtain a first signal in the second light illumination mode, i.e., a zero-order diffraction light intensity distribution in the second light illumination mode, and then transmits to the data processor 35.

[0109] Step three: adjust the aperture of the second aperture stop of the illumination unit 30 to 3011, the illumination mode is the first light illumination mode, and adjust the aperture size of the first aperture stop 341 to the second state 3412. Measure a sample position 5 on the second substrate M2, and the second substrate M2 is pre-provided with a plurality of sample positions 5. The first detector 344 takes a photo to obtain a second signal in the first light illumination mode, i.e., a positive first-order diffraction light intensity distribution, and then transmits to the data processor 35.

[0110] Step four: adjust the aperture of the second aperture stop of the illumination unit 30 to 3012, the illumination mode is the second light illumination mode, and keep the aperture size of the first aperture stop 341 as the second state 3412. Measure the sample position 5 on the second substrate M2, and the first detector 344 takes a photo to obtain a second signal in the second light illumination mode, i.e., a negative first-order diffraction light intensity distribution, and then transmits to the data processor 35.

[0111] Step five: measure another sample position 5 on the second substrate M2, repeat steps three to four until all sample positions 5 are measured. The data processor 35 calibrates the second signal in the first light illumination mode according to the first signal in the first light illumination mode, and calibrates the second signal in the second light illumination mode according to the first signal in the second light illumination mode, and calculates the overlay error of the second substrate M2 according to the calibrated second signal in the first light illumination mode and the calibrated second signal in the second light illumination mode.

[0112] Further, the above measurements are all average values of multiple measurements. The first substrate M1 is a standard bare silicon wafer without measurement marks, or a standard measurement sample such as an aluminum mirror. The second substrate M2 is pre-provided with a plurality of sample positions 5, each of which includes at least four mark units, such as Figure 12As shown, on the second substrate M2 provided with the first measurement mark and the second measurement mark, more units can be designed for improving measurement accuracy, but four mark units are preferred for cost and test requirements. The first mark unit 51 and the third mark unit 53 have opposite preset offset amounts Δ in the X-axis direction, i.e. have preset offset amounts -Δ, Δ in the X direction respectively. The second mark unit 52 and the fourth mark unit 54 have opposite preset offset amounts Δ in the Y-axis direction, i.e. have preset offset amounts -Δ, Δ in the Y direction respectively.

[0113] When the measurement mark is multi-layer, four or more mark units can be preset at the sample position 5 for ensuring accuracy. For example, nine, the preset offset amounts of each mark unit in the X-axis direction or the Y-axis direction can be: -4Δ, -3Δ, -2Δ, -Δ, 0, Δ, 2Δ, 3Δ, 4Δ.

[0114] The data transmitter calculates the overlay error in the X-axis or Y-axis direction at each sample position 5 according to the following formula:

[0115]

[0116]

[0117]

[0118] The positive first-order diffraction light intensity distribution of the calibrated i-th mark unit;

[0119] The negative first-order diffraction light intensity distribution of the calibrated i-th mark unit;

[0120] The positive first-order diffraction light intensity distribution of the calibrated i+1-th mark unit;

[0121] The negative first-order diffraction light intensity distribution of the calibrated i+1-th mark unit;

[0122] A i The asymmetry of the i-th mark unit is defined as:

[0123] A i+1 The asymmetry of the i+1-th mark unit is defined as:

[0124] t is a proportionality coefficient;

[0125] Δ is the preset offset amount of the i-th mark unit;

[0126] - Δ is a preset offset of the i+1th mark unit, a preset offset of the i th mark unit and the i+1th mark unit is equal in value and opposite in direction in the direction of the same axis (X axis or Y axis); and ε is an overlay error.

[0127] In summary, the overlay error measurement device and method provided by the embodiment reduces the influence of the measurement light spot on the overlay error measurement by taking the light intensity distribution of the zero-order diffraction light under different illumination modes as the calibration variable of the light intensity distribution of the positive and negative first-order diffraction light, improves the measurement accuracy, saves the time cost, and improves the work efficiency.

[0128] The above description is only a description of the preferred embodiments of the present application, and does not limit the scope of the present application in any way. Any modification or change made by a person skilled in the art according to the above disclosure is within the protection scope of the claims.

Claims

1. A device for measuring overlay error, characterized in that, The overlay error measurement device includes an illumination unit, a beam splitter, an objective lens, a first detection unit, and a data processor; the illumination unit is used to provide illumination in two or more different illumination modes; the beam splitter includes a first beam splitter and a second beam splitter. The light provided by the illumination unit is transmitted to the first substrate or the second substrate through the first beam splitter and the objective lens, and after being reflected by the first substrate or the second substrate, it is transmitted through the objective lens, the first beam splitter and the second beam splitter to form a first beam, which is then transmitted to the first detection unit. The first detection unit includes a first aperture stop and a first detector. The first aperture stop includes at least one adjustable through hole, and the first beam is transmitted to the first detector through the first aperture stop. When the light is reflected by the first substrate and the first aperture stop is in a first state by adjusting the through hole, the first detector outputs a first signal to the data processor; when the light is reflected by the second substrate and the first aperture stop is in a second state by adjusting the through hole, the first detector outputs a second signal to the data processor. The data processor is used to calculate the overlay error based on the first signal and the second signal.

2. The overlay error measuring device as described in claim 1, characterized in that, When the light is transmitted along the direction from the objective lens to the first aperture stop, wherein, when the first aperture stop is in a first state, the effective first numerical aperture of the objective lens is greater than 0.5; and when the first aperture stop is in a second state, the effective first numerical aperture of the objective lens is less than or equal to 0.

5.

3. The overlay error measuring device as described in claim 2, characterized in that, When the light is transmitted along the direction from the objective lens to the first substrate or the second substrate, the second numerical aperture of the objective lens is greater than or equal to 0.9, and the first numerical aperture is smaller than the second numerical aperture.

4. The overlay error measuring device as described in claim 1, characterized in that, The illumination unit includes a light source, an illumination collimator, a second aperture stop, and an illumination repeater; wherein... The light source is used to provide illumination; The illumination collimator is used to modulate the light provided by the light source; The second aperture stop is used to change the illumination pattern of the light after it has been modulated by the illumination collimator; The lighting repeater is used to transmit light passing through the second aperture stop to the first beam splitter.

5. The overlay error measuring device as described in claim 4, characterized in that, The lighting unit further includes an electric turntable, and the lighting unit includes at least two second aperture stops. The electric turntable is used to switch between different second aperture stops to change the lighting pattern of the light after being modulated by the lighting collimator.

6. The overlay error measuring device as described in claim 1, characterized in that, The first detection unit further includes an imaging repeater and an imaging mirror group, wherein the imaging repeater, the first aperture stop, the imaging mirror group and the first detector are arranged in sequence; The imaging repeater is used to transmit the first beam after it has been split by the second beam splitter to the first aperture stop. The imaging lens group is used to image the first beam passing through the first aperture stop onto the first detector.

7. The overlay error measuring device as described in claim 1, characterized in that, The first signal is the intensity distribution of the zeroth-order diffracted light of the first beam; the second signal is the intensity distribution of the positive first-order diffracted light and the intensity distribution of the negative first-order diffracted light of the first beam.

8. The overlay error measuring device as described in claim 1, characterized in that, Multiple sample locations are selected on the second substrate. Each sample location includes at least four marking units. Each marking unit is provided with a measurement mark. The measurement mark includes a first measurement mark and a second measurement mark. The first measurement mark and the second measurement mark correspond to each other. The first measurement mark is provided with a preset offset relative to the second measurement mark. The preset offset includes a preset offset in a first direction and / or a preset offset in a second direction. The first direction and the second direction are perpendicular to each other.

9. The overlay error measuring device as described in claim 8, characterized in that, Both the first measurement mark and the second measurement mark are gratings. The light transmitted through the objective lens is diffracted by the gratings, producing multi-level diffracted light.

10. The overlay error measuring device as described in claim 1, characterized in that, The overlay error measuring device further includes a second detection unit, which includes an angular spectrum imaging component and a second detector. The light beam, after passing through the objective lens, the first beam splitter, and the second beam splitter, forms a second beam. The second beam is transmitted to the second detector via the angular spectrum imaging component. The second detector outputs a third signal to the data processor. The data processor monitors the energy fluctuations of the light on the first substrate or the second substrate based on the third signal.

11. A method for measuring overlay error, characterized in that, The overlay error measurement method includes: Step 1: Adjust the illumination unit to the first illumination mode and the first aperture stop to the first state; measure the first substrate; the first detector acquires the first signal under the first illumination mode and transmits it to the data processor. Step 2: Adjust the illumination unit to the second illumination mode and the first aperture stop to the first state; measure the first substrate; the first detector acquires the first signal under the second illumination mode and transmits it to the data processor. Step 3: Adjust the illumination unit to the first illumination mode and the first aperture stop to the second state, measure a sample position on the second substrate. Multiple sample positions are preset on the second substrate. The first detector acquires the second signal under the first illumination mode and transmits it to the data processor. Step 4: Adjust the illumination unit to the second illumination mode and the first aperture stop to the second state; measure the sample position on the second substrate; the first detector acquires the second signal under the second illumination mode and transmits it to the data processor. Step 5: Measure another sample position of the second substrate, and repeat steps 3 to 4 until all sample positions are measured; the data processor calibrates the second signal under the first illumination mode according to the first signal under the first illumination mode, and calibrates the second signal under the second illumination mode according to the first signal under the second illumination mode, and calculates the overlay error of the second substrate according to the calibrated second signal under the first illumination mode and the calibrated second signal under the second illumination mode.

12. The overlay error measurement method as described in claim 11, characterized in that, In step one, the first signal under the first illumination mode is the intensity distribution of the zero-order diffracted light under the first illumination mode.

13. The overlay error measurement method as described in claim 11, characterized in that, In step two, the first signal under the second illumination mode is the intensity distribution of the zero-order diffracted light under the second illumination mode.

14. The overlay error measurement method as described in claim 11, characterized in that, In step three, the second signal under the first illumination mode is the intensity distribution of the positive first-order diffraction light at the sample location on the second substrate.

15. The overlay error measurement method as described in claim 11, characterized in that, In step four, the second signal under the second illumination mode is the negative first-order diffraction light intensity distribution at the sample location on the second substrate.

16. The overlay error measurement method as described in claim 11, characterized in that, The first signal and the second signal are measured multiple times and the average value is taken.

17. The overlay error measurement method as described in claim 11, characterized in that, In step three, multiple sample positions are preset on the second substrate. Each sample position includes at least four marking units, and each marking unit is provided with a measurement mark. The measurement mark includes a first measurement mark and a second measurement mark. The first measurement mark and the second measurement mark correspond to each other, and the first measurement mark is provided with a preset offset relative to the second measurement mark. The preset offset includes a preset offset in a first direction and / or a preset offset in a second direction. Among them, the preset offsets of at least two marking units are in the first direction and the preset offset directions are opposite but the values ​​are equal. The preset offsets of at least two marking units are in the second direction and the preset offset directions are opposite but the values ​​are equal. The first direction and the second direction are perpendicular to each other.

18. The overlay error measurement method as described in claim 17, characterized in that, The asymmetry of the marker unit is obtained using the following formula: ； ; The intensity distribution of the positive first-order diffraction light corresponding to the calibrated i-th marker unit; The intensity distribution of the negative first-order diffraction light corresponding to the calibrated i-th marker unit; This represents the intensity distribution of the positive first-order diffraction light corresponding to the (i+1)th unit after calibration. This represents the intensity distribution of the negative first-order diffraction light corresponding to the (i+1)th unit after calibration. The asymmetry of the i-th marker unit; The asymmetry of the (i+1)th marking unit; Wherein, the preset offset on the i-th marker unit and the (i+1)-th marker unit is equal in value but opposite in direction in the first direction or the second direction, and the first direction and the second direction are perpendicular to each other.

19. The overlay error measurement method as described in claim 18, characterized in that, The data processor calculates the overlay error in the first or second direction at each sample position using the following formula: ； The asymmetry of the i-th marker unit; The asymmetry of the (i+1)th marking unit; This is the preset offset; This is due to overprinting error.

Images